Current Li-ion battery technology provides an energy density of ˜150-220 Wh/kg at the cell level when used over the full, 100% depth-of-discharge (DOD) range. To increase the inherent Li-ion cell energy density, there has been a strong focus on the development of new, high capacity cathode materials. One promising class of materials that has been the focus of extensive research and development for several years is the composite “layered-layered” structures, or lithium-rich, Ni—Co—Mn (NCM) oxides, reflecting the fact that these can be viewed as topotactically integrated composites of two different layered phases. The general formula for these cathodes is (1−x)(Li2MnO3).x(LiMO2), where M=Ni, Co, Mn. Some of the optimized compositions have demonstrated capacities of 275-300 mAh/g when charged above 4.6 V and are referred to as high-energy NCM or “HE-NCM,” a huge improvement over the 155 mAh/g of conventional LiCoO2 or Li(Ni1−a−bCoaMnb)O2 layered cathode materials. Such a high capacity cathode has the potential to lead to Li-ion cells with energy densities approaching 250 Wh/kg utilizing conventional graphite anodes. Unfortunately, the HE-NCM cathode materials have a number of inherent impedance, voltage profile, and stability issues that need to be fully addressed before they can be used to make commercially viable high capacity Li-ion cells.
Farasis and its scientists have been working with these materials since the time of their first discovery and much progress has been made in addressing some of these barriers. During this time, Farasis has developed proprietary coatings and electrolyte compositions to stabilize the surface chemistry of these materials and developed electrode formulations and cell designs to improve their rate capability and cycling stability. Recently, a new synthetic route to HE-NCM materials based on low-temperature ion-exchange chemistry was reported that leads to greater power capability and cycling stability while still achieving the very high specific capacities characteristic of this class of materials; the improved HE-NCM compositions synthesized in this way will be referred to as IE-HE-NCM (“ion-exchanged HE-NCM”). These promising results are consistent with over a decade of reports in which ion exchange based synthetic approaches have been used to make layered Li-ion cathode materials with improved performance characteristics. In particular, approaches based on routes in which sodium analogs of various layered Li—Ni—Mn—O materials were synthesized and then ion exchanged with Li to form the active lithium transition metal oxide cathode material have been extensively studied. In some cases, significant improvements in rate capability and cycling stability have been observed.